Representative viruses from the major (M) HIV-1 group (comprised of 10 clades, A-J) have been identified throughout the world, with different clades predominating in different parts of the world. A vaccine developed against HIV will have to be potent against all the clades identified in the different regions of the world. Independent studies have investigated the immunologic relatedness of different HIV-1 clades identified worldwide. Mathematical analysis of immunochemical and neutralization data using sera, monoclonal antibodies (mAbs), viral proteins, and viral isolates from patients infected with different HIV-1 clades worldwide have revealed from seven up to fourteen 'serotypes', or 'immunotypes'. Eight of the ten HIV-1 group M clades (A-H) have been identified in Cameroon, yet, nothing is known on the immunologic relatedness of isolates of these clades compared to those obtained globally. Because Cameroon is one of the locations where cross-species transmission of SIVcpz/HIV-1 appears to have occurred, and because the divergence of the clades may have originally occurred in a few ethnic groups in limited regions of Cameroon (and neighboring countries) where human genetic diversity is limited by cultural and geographic factors, the diverse HIV-1 clades found in Cameroon may be more closely related to one another immunologically than the diverse HIV-1 clades that one now finds globally. To test this hypothesis, that different HIV-1 clades in Cameroon are more immunologically related, and constitute fewer serotypes compared to those obtained internationally, the following specific aims are identified: AIM 1: To compare the immunologic relatedness of group M HIV-1 subtypes (A- H) obtained from Cameroon and those obtained internationally by studying the epitopes that are exposed on the surface of these viruses using anti-gp120 and anti-gp41 mAbs. AIM 2: To define and compare the number of immunologic clusters of viruses obtained in Cameroon with those obtained internationally, and to define the epitopes that define these serotypes by applying cluster analysis to the data generated in AIM 1.